View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Kanazawa University Repository for Academic Resources Detecting Urban Dynamics with Taxi Trip Data for Evaluation and Optimizing of Spatial Planning:The Example of Xiamen City, China 著者 Longzhu Xiao, Wangtu(Ato) Xu, Jixiang Liu journal or International Review for Spatial Planning and publication title Sustainable Development volume 4 number 3 page range 14-26 year 2016-07-15 URL http://hdl.handle.net/2297/45836 doi: 10.14246/irspsd.4.3_14 International review for spatial planning and sustainable development, Vol.4 No.3 (2016), 14-26 ISSN: 2187-3666 (online) DOI: http://dx.doi.org/10.14246/irspsd.4.3_14 Copyright@ by authors, SPSD Press from 2010, Kanazawa Detecting Urban Dynamics with Taxi Trip Data for Evaluation and Optimizing of Spatial Planning: The Example of Xiamen City, China Longzhu Xiao1 Wangtu (Ato) Xu1* and Jixiang Liu2 1 School of Architecture and Civil Engineering, Xiamen University 2 School of Urban Planning and Design, Peking University * Corresponding Author, Email: [email protected] Received: 31 August, 2015; Accepted: 15 January, 2016 Key words: Taxi trip data, Urban dynamics, Spatial planning, Xiamen Abstract: Commonly, it is very hard to examine underlying urban dynamics due to rapid spatial expansion and land use variations. In this paper, the origin-destination (OD) data extracted from taxi trip data collected in Xiamen, China, covering 30 days was utilized to detect the underlying dynamics of Xiamen City. Specifically, we discretized the study area into 400m*400m grids so that the number of originating points and destination points of the taxi trips could be counted separately within each single grid. Then, heat maps of the taxi mobility were made to achieve a general understanding of urban dynamics. Secondly, we took advantage of the concept of complex networks to analyze the daily taxi trip data. Using a method of community detection, we divided the study area into six main sub-regions called functional self-sufficient zones (FSZs) in which spatial associations are tight and dense. The features of these FSZs helped us to gain a deeper understanding of urban dynamics. Finally, based on this understanding, we further evaluated and optimized the urban spatial planning of Xiamen. Balancing land use allocation was suggested to enhance the multi- centric structure and reduce congestion. This study provides a relevant contribution by exploring the potential of applying taxi trip data to identify urban dynamics revelations and urban planning optimization solutions. 1. INTRODUCTION Spatial planning is the most traditional and widely used planning paradigm used in urban planning processes, especially in Asian countries. Compared with modern western urban planning, which quantitatively analyzes and solves urban problems through building a vigorous index system (Alexander, 2000; Benevolo & Landry, 1967), spatial planning in China has been relatively more subjective and drawn from much attention to aesthetics. Traditional spatial planning has been trying to manage individual travel behavior by means of mere construction of physical environment. However, such arrangements on future city life seem to fail in achieving the goal of “better cities” that the political and professional elites have expected. This kind of failure has aroused wide discussions in academia. On the other hand, there is still little empirical research evaluating and examining the rationality and effectiveness of proposed urban planning objectives and quantifications 14 Xiao, Xu, & Liu 15 in China. The sharply expanding urban scale, increasing unpredictability and complexity, have made understanding urban dynamics more difficult. Fortunately, in recent years, the availability of big geospatial data, such as cell phone data, public transportation card records and taxi trajectories, has boosted research on the detection of urban dynamics (Lu & Liu, 2012). Compared with other public transportation, such as bus and metro, which are constrained to prescribed routes, taxis can travel freely to reach different places where other public vehicles cannot get. Moreover, taxi trip data can reflect people’s activities through information related to the spatio-temporal connections of origin and destination. Taking advantage of the diversity of routes as well as accurate spatio-temporal information, taxi trip data offers a richer and more detailed glimpse into human mobility patterns (Liang et al., 2012; Wang et al., 2015). Moreover, human mobility studies based on taxi trip data have been applied in many fields, such as traffic management (Yuan, N. J. et al., 2013), urban structure detection (Liu, X. et al., 2015), and land use analysis (Pan et al., 2013; Peng et al., 2012; Yuan, J., Zheng, & Xie, 2012). But a lot of relevant research tends to analyze taxi trip data from the pick-up points and drop-off points in separation. Thus, the spatial interaction of the mobility is omitted. Furthermore, there has been little research applying taxi trip data to evaluate and optimize the urban spatial planning scheme. Most of the existing studies focus on exploring the human behavior and mobility information from taxi trip data. Among research of individual travel behavior and urban dynamics, the complex network concept has been widely used to detect spatio-temporal connectivity relationships. Due to that, “community” is the most important concept, or structure, in both the individual network and overall urban plan, as it has been evaluated intensively in complex network studies. Newman and Girvan (2004) defined the community as “a sub graph containing nodes which are more densely linked to each other than to the rest of the graph”. In the context of urban planning, community is able to demonstrate the underlying dynamics of cities, which are often omitted or surmised subjectively by traditional planning. As community detection can be considered a process for dividing complex networks into several sub networks, among which the internal connections are extraordinarily closed, many researchers have emphatically studied the formation process of communities. Gao et al. (2013), Roth et al. (2011), Liu, Y. et al. (2014), Austwick et al. (2013) and Liu, X. et al. (2015) all focused on this topic, however, all of these researchers failed in evaluating the urban practices with revealed urban dynamics phenomena. In this paper, the origin-destination (OD) data extracted from the taxi trip data collected in Xiamen, China, covering 30 days was utilized to detect the underlying dynamics of Xiamen City. Specifically, we divide the study area into 400m*400m grids so that the number of originating points and destined points of the taxi trips could be counted separately within every single grid. Then, heat maps of taxi mobility were made to achieve a general understanding of urban dynamics. Secondly, we took advantage of the concept of complex networks to analyze the daily taxi trip data. With the method of community detection from complex network theory, we detect six communities, which are named functional self-sufficient zones (FSZs) in the study area. The features of these FSZs helped us to gain a deeper understanding of urban dynamics. Finally, based on this understanding, we further evaluated and optimized the urban spatial planning of Xiamen. This paper has been organized as follows, in the following section the methodology for community detection is presented, then, following is the case study section in which the proposed methodology is applied to detect the 16 IRSPSD International, Vol.4 No.3 (2016), 14-26 community of Xiamen City based on its taxi trip data. Following this, the discussion and conclusion are provided. 2. METHODOLOGY 2.1 Study area Xiamen City is a coastal city of Fujian province, China, and one of the special economic zones opened to international investment when China started its economic reform in the 1980s. Since the 2000s, Xiamen has developed from an island city to a coastal bay city. Two out of six administrative districts lie on Xiamen Island, which is the central business district (CBD) of Xiamen City. The other four administrative districts are located on mainland areas. The urban configuration of Xiamen City is shown in Figure 1. According to the Master Plan of Xiamen City (2010-2020), there will be two CBDs by 2020. Regarding the transportation system of Xiamen, currently, there are two railway stations and an airport in Xiamen. In addition, an airport is under construction and will be in operation by 2020 in Xiang’an district. There are also the metro system, which is currently under construction, and three lines which will be put in operation by 2020. Regarding the taxi system, the total number of taxi cars is about 7,500. They account for a large proportion of the travels inside the city. Figure 1. Study area of Xiamen 2.2 Study framework With the help of analysis methods based on community detection and complex network theory, this research expects to solve the following three problems: Xiao, Xu, & Liu 17 1). How will taxi trip data help us to achieve a general understanding of urban dynamics? 2). How can we take advantage of the complex network built based on the origin-destination (OD) data which were extracted from the taxi trip data to better understand urban dynamics? 3). How can proposed urban land use planning be guided and enhanced based on the underlying urban dynamics revealed by taxi trip data? It has been shown that taxi trip data could not only reflect a large proportion of individual travel habits, but also, it is used as a data source for research on urban dynamics. Accordingly, the following analytical framework is designed to solve the problems above. As shown in Figure 2, we firstly obtain a general understanding of urban dynamics according to the spatial distribution of taxi trips data. Then we extracted daily taxi trips from taxi trip data. Secondly, we built a network using the daily taxi trips and analyzed this network using a method of community detection to display the underlying principle of the urban dynamic.